1. Field of the Invention
This invention is in the field of valve train or valve operating mechanisms for internal combustion engines and more particularly variable valve timing and valve lift mechanisms.
2. Description of the Prior Art
The desirability of varying valve timing and valve overlap; i.e., the angle of rotation of the crankshaft of a reciprocating internal combustion engine during which both exhaust and intake valves of a cylinder are open, as a function of speed and load to optimize the efficiency of a reciprocating internal combustion engine under any given operating condition has been recognized. The prior art solutions teach the use of a valve train including a single lobed cam on a rotating cam shaft with a tappet engaging the lobed cam to convert circular motion to reciprocating linear motion of a tappet which is operatively connected directly to a valve as in an overhead cam shaft type engine or through a rocker arm. A heavy duty spring biases the valves closed and the tappet against the cam surface. Changes in timing are accomplished by changing the length of an element in the valve train, the location of the cam shaft lobe to the tappet, or by varying the axis of rotation of rocker arms.